The synaptic organization and physiological responses of retinal neurons are fairly well understood. Much less is known about the role of glial cells and their interaction with retinal neurons. We are interested in understanding the function of glial cells, particularly the Muller cells, in the vertebrate retina. The present research proposal has three main objectives: (1) to isolate Muller cell-specific monoclonal antibodies which are useful for separation and identification of Muller cells in the retina or in cell cultures of retinal glia. Retinal membranes or Muller cell-enriched fractions will be used as immunogens, and screening will be carried out by indirect immunofluorescence on aldehyde-fixed, cryostat sections; (2) to obtain Muller cell cultures from retina and to study the uptake and relase of retinal neurotransmitters, glutamate, aspartate and GABA; and (3) to examine the basis for glial fibrillary acidic protein (GFAP) expression in Muller cells undergoing reactive gliosis. RNA blotting and in situ hybridization studies will be carried out to address this question. In addition, the ability of Muller cells to proliferate in gliosed retinas will be investigated using a combination of 3H-thymidine autoradiography and immunocytochemistry. These experiments should enable us to understand the functions of Muller cells in the retina and how their dysfunction might lead to diseases such as cystoid macular edema.